FIG. 2.

The first intron of the mdm2 gene contains a T3-dependent response element. HeLa cells were transfected by electroporation with 5 μg of Cosx1CAT or the indicated deletion mutants of Cosx1CAT with 4 μg of a vector expressing cT3Rα. Cosx1CAT contains a 1-kb XhoI-XhoI fragment from the first intron of the murine mdm2 gene cloned upstream from the adenovirus major late TATA box-TdT initiation signal-CAT gene sequence (67). Following transfection, cells were incubated for 48 h without or with 500 nM T3 prior to determination of CAT activity.